Propulsion theory

Propulsion theory is the branch of physics and engineering that studies the principles, mechanisms, and technologies used to generate a force (thrust) to move an object forward through a medium (like air or water) or through the vacuum of space.

It is fundamentally based on Newton's Third Law of Motion: "For every action, there is an equal and opposite reaction." Propulsion systems work by accelerating a mass of working fluid (air, water, exhaust gases, or ions) in one direction, causing a reaction force (thrust) to push the vehicle in the opposite direction.